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Cable Faults: A Fact Of Life For Power Distribution Utilities

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Published: Friday, 24 March 2017 09:36

Damon Mount of Megger explains the benefits of using a new compact and easily transportable cable fault location system for dealing efficiently and effectively with problems on underground power distribution cables.

Most local distribution cables in towns and cities are buried underground with other services as it is practical and desirable to install them away from public access and out of sight. However, cable faults are one of the main causes of power outages. So what happens if an underground cable develops a fault?

It’s likely that fault will trip the protection devices and one or more customers will lose power. The power distribution utility is then in a race against time to find and repair the fault so that the customers can have power restored, and the utility isn’t penalised heavily for loss of supply.

But where is the fault? The cable may be many hundreds of metres or even kilometres long. It is therefore invaluable to have a fault locator that can tell the engineer the distance to the fault and pinpoint its exact location in the field. Otherwise it’s down to digging lots of trenches to find the fault – which, of course, is disruptive, time-consuming and expensive.

To tackle the challenge of finding cable faults quickly and accurately, many power distribution utilities use the Megger EZ-Thump cable fault locator as part of their first response. It’s a quick and relatively low cost method of finding cable faults on the distribution network. In the event of a cable fault, the battery-powered EZ-Thump and a Digiphone pinpointer can easily be taken to site in the boot of a car. The EZ-Thump is small (36 x 39 x 50 cm) it is the ideal first step in finding a cable fault.

If the fault can be found quickly, it can be rectified and the power turned back on with minimal expense and with minimal disruption to the customer. This time saving alone will effectively pay for the unit within a few uses.

In the experience of one power distribution utility, trials with the EZ-Thump resulted in nearly 100% of faults being found on the utility’s 11 kV network, saving a huge amount of time and money, as it allowed them to restore the power to more customers more quickly. The utility also saved money in penalties for Customer Minutes Lost, improved its performance statistics with the regulator and its reputation with customers.

There are, of course, some faults that might not be found by the EZ-Thump, as they require higher energy to break down. In that case, a more powerful fault location system or test van must be brought in. Power distribution utilities can, however, buy many EZ-Thumps for the price of a test van, and these will give them greater coverage and a faster response rate, albeit with a more limited capability.

The EZ-Thump’s simple operating system guides the user through the fault location process, allowing a wide range of individuals to use it; so there is always someone available to respond to an outage.

Moreover, the EZ-Thump and test vans are complimentary. The combination of the two methods has led to a massive improvement in response times. Increased geographical coverage with the EZ-Thump with back up support from larger fault locating systems has revolutionised cable fault location in the distribution network.